We propose a comprehensive program project to investigate in broad perspective the relationship of immunity functions and cancer. To study the role of the immune system in the growth and regression of malignant cells, we will make concerted efforts in several areas of research emphasizing: (1) fundamental analysis of primary and secondary immunodeficiency diseases; (2) elucidation of perturbation of immunity functions in malignant diseases; (3) investigation of the effects of genetic factors on the expression of immunity functions; (4) in-depth analysis of the development of lymphoid system and of immunity functions; (5) dynamic interactions between malignant cells and host-immunity responses; and (6) development of methods to enhance and suppress immunity against cancer. Separate investigations will be closely integrated with one another and with other major programs and projects within the Memorial Sloan-Kettering Cancer Center, with the ultimate goal being to develop to a maximum capacity to utilize immunologic knowledge in the control of human cancer.